ME458 Lab 4 8/17/2000 page 1
ME458 Noise Control
Laboratory Exercise #4
Acoustic Materials and NC Rating of Rooms
Objectives:
1) Measure the sound absorption coefficients of porous materials using a standing
wave tube (Impedance Tube)
2) Determine the NC rating of several spaces and compare to recommended values
Part 1: Acoustic Materials
Using the B&K impedance tube, determine the normal incidence absorption coefficient,
statistical absorption coefficient and the impedance for 2 different materials. Compare
your results to published values of absorption coefficients.
Material:
Freq Hz Lpmax Lpmin D
1 D
2 αn Z/ρc αstat Published
value of α
125
250
500
1000
2000
Material:
Freq Hz Lpmax Lpmin D
1 D
2 αn Z/ρc αstat Published
value of α
125
250
500
1000
2000
List of Formulas Used:
αn=
Z/ρc=
αstat=
